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The Film Look on a Budget

This article describes how modern 35mm adapters have enabled a new range of 35mm optics to be used on popular consumer and prosumer camcorders to very good effect.

They are an ideal solution for those on a tight budget hoping to achieve the look of quality production values and a shallow depth of field. Budget constraints have meant that until now solutions have been limited.

Factors which influence the Depth of Field

Simply, these can be summarised with 3 easy learning points (see Appendix 1 for explanation why):

Shoot on a camera with a large image sensor

The larger is the image sensor, the shallower is the depth of field (DoF) For an equivalent image, aspect ratio and iris setting: This means that images shot with 35mm cameras or 1” digital sensors (e.g. RED) will have a shallower depth of field than equivalent images shot with 2/3” cameras (e.g. Sony HDW-F900R) and these images will have a shallower depth of field than equivalent images shot with 1/2” digital sensors (e.g Sony .EX-3) and these images will have a narrower depth of field than images shot with 1/3” digital sensors (Panasonic HVX-201/HVX-171) and these will have a shallower depth of field than images shot with HDV Cameras with a ¼” CCD block (e.g. HVR-Z1).

Put simply, shooting on 35mm film (or RED) will, for the same image and aperture, give you a shallower depth of field than a camera with a smaller sensor area.

Shooting the same image with the same aspect ratio on a mini HDV camera will give you a proportionately wider DoF.

The other way of doing this is to shoot on a Digital SLR (DSLR) system, such as the Canon 5D MkII or EOS 7D or equivalent. The difficulty here is that although the image quality can be stunning and the depth of field shallow, you are likely to have problems with:

Panning (due to the constraints of the camera using a rolling shutter which makes vertical lines skew);

Audio – stills cameras only have very basic audio capability, nor professional inputs, difficult to adjust audio levels etc; There are now boxes available which can correct for this.

Monitoring – no professional HD-SDI outputs from DSLR Cameras (as yet anyway). Consequently, external monitoring will be via HDMI output. Also current DSLR cameras mute the camera’s own viewfinder when an external monitor is connected, so you cannot monitor simultaneously the camera viewfinder and a Director’s monitor.

Operating – There is no standard HD viewfinder on Digital SLR cameras as there is on professional video cameras; Zacuto make viewfinder lenses whereby the mount sticks to the LCD panel.

Fitting matte boxes, shoulder sets etc – these are not designed for production but many options now exist to make this easier;

Editing – DSLRs do not (as yet) permit you to shoot in a native editable video format. This may change as time progresses but not when this article was written.

Multicamera syncing – There is no facility for accepting external timecode or external gunlock at present, so shooting in a multicamera environment

There is also a fundamental difference between HD camcorders and DSLR cameras with manipulating the shutter speed. With conventional cameras you can change the amount of motion blur by changing the shutter speed [in film this adjustment is called the gate angle],so by increasing the shutter speed from 1/50th second will increase blur whilst decreasing the shutter speed will decrease the blur. DSLR cameras in motion picture mode currently have fixed shutter speeds of 1/50th second and 1/100th second and consequently ‘swish pans’, so without further options, rapid movements are likely to be seen as juddery.

If you are reading this article, then it is likely that you are not currently shooting on 35mm film, RED or DSLR, but would like your pictures to have a more ‘film look’. You have a number of options to help you to achieve this:

Manipulating Focal Length and Iris to reduce the Depth of Field

It is a basic photographic principle that depth of field decreases as aperture increases. (all other things remaining constant).

It is a basic photographic principle that Depth of Field decreases as focal length increases (all other things remaining constant)

Therefore, to decrease your DoF, you have two fundamental options, or other “additional” tools to achieve this:-

1. Adjusting the Iris

By reducing the amount of light entering the lens, you can open the iris and this will subsequently reduce your depth of field. This can be achieved by inserting Neutral Density (ND) filters in front of the lens, reducing the amount of light entering it. In doing so, to maintain the correct exposure of the image you will need to open the iris and in doing so the depth of field will narrow. A polariser will also reduce the light entering the lens as well somewhat.

The amount that you can do this will be ultimately limited by the ‘speed’ (or Maximum Aperture) of the lens that you are using. ‘Faster’ lenses (i.e. lenses with a smaller F or T number) mean that you have more scope to create shallow DoF images.

'Speed' of the lenses and therefore their capability of opening up to a wider stop

Lenses are classified by their 'speed' rating and this 'F' or 'T' rating gives an indication of how large the maximum iris of the lens is. The smaller the number, the faster is the lens, so the more light the lens can let through to the sensor.

This also means that when comparing lenses with the same focal length, the one with the smaller minimum F stop or T Stop (i.e. T1.3) will be capable of shooting shallower depth of field than the other with a larger minimum F Stop. i.e. a 20mm T1.4 lens is capable of achieving a shallower DoF than a 20mm T2.8 lens. (though it is worth mentioning that these different lenses working at the same F stop and focal length will achieve the same depth of field – i.e. two lenses of both 25mm – one being a F2.8 lens and the other a T1.4 lens but both working at the same F2.8 setting, will have the same DoF).

This means that using a faster lens creates a greater opportunity for creating narrow depth of fields than using slower lenses.

2. Adjust the Focal Length

Depth of field is affected by the focal length of the lens. Put simply, “zooming-in” will narrow the Depth of field for the same iris setting.

By using the longer end of the lens i.e. zooming in, you will increase the focal length of the lens that you are using and the Depth of Field will reduce. To maintain the similar shot you will also have to move further away from the subject, though the perspective will then alter.

This means that if you are shooting on an HDV Camcorder with 3 x 1/3" or ¼" CCDs, then the options for achieving a shallow depth of field are very limited using any built-in lens on a smaller image-sensor camera.

It is important to mention that in certain circumstances there can be an unintended consequence of adopting this approach whereby the background is ‘compressed’ which changes the perspective of the images somewhat.

If you want to throw the background out of focus to achieve a more filmic look, then you can use a lens adapter of some kind and use additional lenses with the adapter, which leads nicely to:

3. Use 35mm lenses with a suitable adapter

Using a suitable adapter will permit you to fit 35mm stills or motion picture lenses to your digital video camera and shoot the same images as on 35mm film, including creating the same shallow depth of field possible on 35mm film.

There are a number of 35mm lens adapters which permit you to attach 35mm lenses to smaller cameras.

Effectively, there are two different types of 35mm lens adapter:

1. 35mm lens adapters without optical correction

Fitting a lens mount converter without any optics allows you to fit 35mm lenses to digital camcorders. This sounds great and it is inexpensive however, as the saying goes, if it sounds too good to be true, then it probably is! As with the saying, this system doesn’t really work effectively.

This is because in this example you are using lenses which project an image size of about an inch (35mm) onto a much smaller digital image sensor (usually 1/4"-1/2").

Although the theory is lovely, it is of limited use without some form of optical correction to "match" the taking and receiving format sizes. Otherwise you get an effective equivalent field of view of up to 4 times that of the original lens which doesn’t really make this solution practical – see image above.

Another issue with systems like this is that the image landing on the sensor from the lens will also be upside down! This requires that viewfinders and location monitors etc are also inverted to see the image the right way up. Additionally the rushes need to be “flipped” again in post but is an added hassle which does not exist with other adapters which include this correction in their design.

2. The better 35mm lens adapters with optical correction

The second way involves attaching a 35mm lens mount either to the front of the camera or to the camera’s lens and works by focussing the image of the 35mm taking lens onto a ground glass or fine screen which either vibrates or spins. What is important here is that the screen is actually the same size as a 35mm negative, so the image will have the same DoF characteristics as if it was shot onto 35mm film.

The result of using these adapters is that conventional 35mm lenses (and the images they produce) are effectively “re-photographed” onto whatever sensor size your digital video camera has. This gives the "35mm DoF look" onto (almost) any sensor size.

It actually works very well, creating images on the screen with a ‘filmic’ look as if shot on film. However, as is often the case, you never get something for nothing and there is a price to be paid for this:

Firstly, filming through this combination of lenses causes some light loss (up to one and a half stops, depending on type), which reduces the sensitivity of the camera. This can make this combination unsuitable if filming in extremely low light situations and may mean that you need more light on set.

Secondly, the optics in the lens adapter cause additional “softness” to be introduced in the resulting images. Since this may well be the look that you are after anyway, this may not be a problem, but our advice would be to test prior to shooting.

This kind of lens combination can make the camcorder physically a bit clumsy by extending its length somewhat. This is often not a problem, since film primes are usually quite a lot shorter than HD zoom lenses, but worth considering nonetheless, especially if you are in small or enclosed locations.

The speed setting of the rotating disc must be set to a compatible rate to the frame-rate & shutter speed of the camera. Setting the revolving speed too high can cause the adapter to overheat and become noisy (if used for prolonged shots without letting the unit rest between takes) and setting it too slowly can cause the rotating glass 'grain' to be visible. Worse still, forgetting to switch the unit “on” into spinning mode will cause visible 'grain' in the image which will not change, thereby causing 'dirty' images to be recorded which are subsequently unusable.

These adaptors introduce an additional path length to the light falling onto the sensor, which means that these 35mm adapters are prone to flare – especially if panning across sunlight or other highlight sources. This means that the operator must be especially careful to matte the lens properly to avoid this. Be aware that proper production matte boxes are usually supplied with inner ‘mattes’ to screen unwanted light for this very purpose, so ensure that you use them!

Finally, the setting up of a 35mm adapter when using the cameras’ own built-in lens can be a bit tricky to set up correctly. Incorrectly setup systems can cause vignetting (the outer regions of the lens have some shading), visible noise or soft images, so some care is required.

However, when you achieve the correct setup with this combination, the results are truly spectacular! http://vimeo.com/949666

It is worth mentioning here that some work slightly differently but they are described in detail below.

TYPES OF 35MM DoF Adapters

P+S Technik Pro 35 Adapter

It is always good to begin with the best system, so the P+S Technik Pro35 is designed exclusively for 2/3” professional cameras

P+S Technik make an industry-standard adapter called a Pro35 which allows motion picture and stills lenses to be mounted onto 2/3" digital video cameras, such as the Sony HDW-F900R etc.

These are usually fitted with the combination of a PL mount for mounting motion picture lenses. The combination of these lenses in addition to the Pro35 adapter make an expensive combination and usually more expensive than a standard set of HD Prime lenses.

A 1.5 stop loss is usually quoted for this adapter but it is a subject of much debate, so again, test before use!

Low Cost 35mm Adapters

Low-cost 35mm adapters are available for semi-professional/prosumer camcorders such as the Sony Z1/Z5/Z7, EX1/3 or Panasonic HVX 171/201 etc such as the Letus, Mini-35, Red-Rock, Movietube, Brevis and others.

Some of these are better-built than others and the standard is set by the excellent German engineering of the P+S Mini-35 unit. However, others are very much cheaper to purchase than this but they are less robust and are not designed to withstand the punishment of surviving a rental environment, which explains why they are not commonly available to hire from rental companies.

The exception to this is the excellent Letus Ultimate adapter – in our opinion (and we have tried many!), this is as solidly built as the P+S unit and offers superior versatility and value for money compared with the P+S Mini-35 adapter. Consequently, at VMI we have invested in P+S Pro 35 for the larger cameras and a fleet of Letus Ultimate adapters for the smaller cameras. It is worth mentioning that these adapters are developing all of the time and new innovations such as the Cinemek are worth considering too.

If however, you choose to purchase one of these units exclusively for private use, then the low cost units will deliver a shallow depth of field in common with the all of these units but do be wary of the fragility of the low-cost units. Horror stories are frequently heard of lightweight low-cost units simply falling apart on location, so extreme care is required during transport and operation!

There are many of these units available and this article does not seek to provide an exhaustive list. Also, since specifications are liable to continual change and improvement from all manufacturers, I apologise in advance for any inaccuracies written here, though I have done my best to ensure accuracy at the time of writing.

1. P+S Technik Mini-35

The original adapter for small cameras.

The P+S Technik Mini 35 adapter which is designed to work with consumer/prosumer Digital camcorders such as the Sony Z1, Z5, Panasonic HVX-171/201 etc.

When used with these camcorders, the optical path passes through the 35mm lens, the Mini35 adapter and also the camera's own built-in lens as well.

Each camcorder model requires a custom interface to fit the individual camcorder model which work out at around £1,000 each, so it is very expensive to accessorise these units for multiple cameras.

The P+S Technik Pro35 ½? is a special version of the Pro35 designed for ½? Camcorders such as the EX-3 which have non-standard interchangeable lens mounts and also avoid the need for the camera’s own lens. Due to their high cost, they are not yet commonly available.

Another negative to the Mini-35 is that the stop-loss of light is far greater than equivalent systems such as the Letus or Cinemek.

Whilst very good, these adapters are surprisingly expensive – especially if you want multiple camera mounts to interface to it.

2. Letus Adapters

The original Letus Extreme was a poorly made adapter which suffered from frequent back focus shift which made it a very unreliable unit as it would not hold focus without continual adjustment. My advice is to stay away from this model!

Letus then brought out the Letus Ultimate model which was manufactured to much higher standards than the original and this is the unit of choice for VMI.

In common with the P+S Technik Mini-35, this works by focussing the 35mm image onto a rotating ground glass and then passing through a relay optical system to focus onto the camera’s imaging block. Light loss through the basic unit is around ½ stop.

There are other lens options for this to avoid using the camera’s own lens which Letus call ‘relay’ lenses. This means that the Letus adapter can completely replace the camera’s own lens on the Sony EX-3 and others or indeed replace the Pro-35 adapter for 2/3” work, though these are surprisingly expensive.

The main advantage of using the Letus Ultimate adapter is their solid build quality and reliable operation. Also the adapters to fit these to multiple camera models are much more affordable. http://www.letusdirect.com/

3. RedRock Adapters

Redrock Micro produce an extremely low cost adapter which is rather flimsy and not suitable in our opinion for rental or mainstream production use. They work very similarly to the Letus and Mini-35 units but as a consequence of their mantra of being ‘affordable’, this in our opinion makes for a less robust design and rules them out for everything except owner operators. http://www.redrockmicro.com/micro35.html

4. Brevis

The Brevis MP.2 is an extremely lcost, ultra-lightweight 35mm adapdesigned for small cameras with a 37mm filter thread, though it has adapters to work with larger cameras.

It contains an oscillating image plane and its website promises the lightest weight lowest light-loss product. It is available with a non-flipped image or a corrected flipped imaging module.

5. Kinomatik Movietube

Sometimes, you have a unit which really looks the part and delivers great results but isn’t very popular and sadly the Movietube is one of these. It is instantly recognisable in the way the camera is mounted at an angle of 45 degrees making the overall unit shorter than competing models.

The build quality and performance of these units is absolutely superb. Furthermore, they are designed without any moving parts, which is a real advantage in not having to worry about power or worrying about the motor failing, which has been a problem with certain designs of adapter.

They achieve this by providing a fine microcrystalline screen to focus the image which is not resolved by HD resolution and still corrects the image optically, but one disadvantage to this is that in the original version more than 1.5 stops of light were lost. The latest screens and lenses are faster and have improved this.

The ST system is equipped with a Sony Broadcast grade viewfinder so that you can monitor pin-sharp images and also incorporates a built-in shoulder mount kit. However, carrying all of these items also makes the camera kit larger and more unwieldy than the other systems and some users complain that they are difficult to operate. However, the need for professional power for the viewfinder does work in ones favour when balancing the system for shoulder mount use. You never get something for nothing and the high cost of these system makes them expensive to use and rent compared with competing systems

Saying all the above however, we have had some excellent results shooting with Cooke S4i lenses with Panasonic HVX-171 cameras.

Recent innovations have brought about the micro-crystalline screen and they are developing this product to work with larger image sensor cameras. http://www.movietube.de/

6. Cinemek G35

Like the Movietube , the Cinemek also utilises a focusing screen with a fine chemically etched focusing screen structure so that it does not need a spinning glass.

The major issue with systems like this is that as with the other lower cost adapters, is that the projected image from the lens will also be upside down! This requires that viewfinders and location monitors etc are also inverted to view the image the right way up. This also means that the images are recorded inverted too, which can be corrected in post but is an added hassle which does not exist with the other adapters which include this correction in their design.

This is the latest development of adapter and it is too early to say how reliable this is or how well it works but the image looks cool! The companies website claims that a full set of rails, mounts and accessories are currently being developed. http://www.cinemek.com/g35.php Other systems exist such as the SG Blade, of which some do not correct for inverted images etc but in our opinion, you get what you pay for!

Shoulder-mount kits and bridge plates

One of the issues with having a tube with weighty optics, follow focus, matte box and potentially filters as well on the front of a camera, is that the centre of gravity is completely pushed forward which makes hand-held operation difficult.

For this reason, there are a range of sliding base plates available (or bridge plates) which allow you to move the camera position on the tripod to correct this. They also usually include a 15mm bars system on which to mount your peripherals such as follow focus and matte box.

However, if you are working hand-held, then you need a shoulder pad with a camera mount plus hand grips and the disadvantage here is that all of the weight is thrown to the front.

Some of these products have experimented with putting heavy batteries at the rear in order to balance this rig and it is easy to see how this can help.

At VMI, we are experimenting with using combinations of shoulder kits, Blue Modular kits, Zacuto rigs and Easyrigs to minimise fatigue for totally hand-held shoots.

Types of 35mm Lenses

Motion Picture Lenses

Motion picture lenses have had decades of refinement until they have reached the point today of near perfection!

There is a huge range of lenses which offer excellent optics, robust casings, beautifully smooth mechanics, zero focus breathing etc but the limited numbers for production and high build quality means that they are usually out of reach for budget productions.

Consequently, I do not want to spend much time on this group of lenses, as stills lenses offer the greatest ‘bang for your buck’ but if you would like to learn more, see the appendix section Motion Picture Film Lenses.

Shooting with stills lenses

Stills lenses are a much lower cost option of lenses than motion picture lenses but because they are built for stills and not motion picture use, there are several compromises to be made. Happily, there are also several solutions too!

If you buy a quality stills prime set such as Nikon or Canon, then you can expect great image quality at a stills price. In contrast, a set of Cookes or UltraPrimes will cost up to £100,000 compared with approximately £5-7,000 for an equivalent set of stills prime lenses.

There are some challenges though to using stills lenses for video work.

Firstly, modern digital SLR cameras tend to be fully automatic and all of the lens controls are operable from the camera. Consequently, over time, the manual functions began to disappear from stills lenses, so that today many lenses available to buy do not have a manual iris ring, which makes them useless for the lens adapters above.

Problems with using stills lenses for video applications

Stills lenses aren't built to withstand the rigours of motion picture film production, which means that they are built in much more lightweight lens housings. As a result of this, the screws holding a lens together are not designed to withstand the forces applied when using follow focus units etc. If you use a lens control system to control the focus, then the power of the servo units is sufficient to rip the screws of a stills lens apart!

There is no focus gear on stills lenses. This means that you can’t drive the focus mechanism with a follow-focus unit. You can install an external focus gear using the Zacutto Zipgear system or custom modify lenses (like VMI do), which effectively straps a gear onto the outside of the lens to be driven by a follow focus unit. The downside to doing this is that the focus adjustment of small lenses means that you only have a small amount of adjustment of the focus ring over the entire range of the lens. In other words, your focus puller will complain if you use this combination!

The focus thread runs in the opposite direction to motion picture film lenses, so your focus puller either needs to learn to pull focus in the opposite direction, or alternatively use a follow focus unit with an idler gear, which reverses the motion of the follow focus correct for stills lenses. This correction gear is built in to the new ARRI MFF1 follow focus units.

Differing lens diameters meaning standard clip-on matte boxes won't fit – besides which the lens will not be strong enough to hold a clip-on matte box without putting undue pressure on the lens mount and housing.

Stills lenses have multiple non-compatible lens mounts to Motion Picture lenses, so you will need to fit suitable adapters to work with existing cameras and 35mm lens mounts. Nikon uses a ZF mount and there are many more standards including 2 alone for Canon. These mounts are also not as secure as PL motion picture lens mounts or B4 video lens mounts.

They are designed for portability, so some lenses ‘breathe’ and so when changing the focus of the lens, the image can noticeably resize, resulting in ‘Focus Breathing’.

There are many fully-manual older prime lenses available second hand which are completely suitable but at VMI we chose the excellent Zeiss ZF series prime lenses which have fully manual operation and for which we have made some custom modifications to make them work better in video applications.

Even considering all of the above, if you have a low-budget short film and want to narrow the depth of field of your images and are using a low-cost camcorder, then it is still worth considering a set of stills primes to work with your system.

Be prepared for your crew to complain audibly about having to work with non-standard lenses or adapters and above all, be gentle with the equipment! You don't want them falling apart on you whilst in production (or indeed at any other time either!).

Solutions to using stills lenses for Video – Zeiss ZF Distagon/planar set

At VMI we have chosen the Zeiss ZF series lens sets for our Letus kits, as in our opinion they offer the best compromise for budget applications of performance and quality.

The Zeiss Planar and Distagon design use the same lens arrangements which have been proven in the World-acclaimed Zeiss SuperSpeed, DigiPrime, UltraPrime and MasterPrime lenses.

The ZF series lenses are the same high quality optics re-housed as used in the new ARRI lightweight 35mm lenses, except they cost ¼ of the price!

VMI have modified the lenses to fit a custom follow focus ring which is a larger diameter than the lens, to give the focus-puller a greater range of adjustment.

VMI have also custom-fitted lens fronts so that the entire set shares a common 80mm lens diameter and can be used with common matte-box donuts for ease of use.

VMI supply the ARRI MFF1 follow-focus unit which includes a reversible gear, so that the direction of rotation is corrected during operation automatically.

The lenses are very fast (T1.4 and T2) to allow the Cinematographer easier depth of field manipulation.

These lenses include the commonly available Nikon ZF mount which allows them to be fitted either to Nikon stills lenses or threading adapters for other stills lenses or 35mm lens adapters such as Letus etc.

The VMI-Letus 35mm package

The package includes the ARRI MFF1 follow focus with reversible focus gear, bridge plate and also ARRI MMB1 matte box.

The system is designed to work with VMI-modified Zeiss ZF Series lenses but will also work with other stills primes or PL-mount Motion Picture lenses and VMI offer a package including a set of ZF Series lenses

Shooting with B4 Prime/cine lenses with EX-3

Another approach to achieving filmic results is to use a suitable ring adapter (such as the Fuji ½” -2/3” adapter for the EX-3) and use Broadcast HD 2/3” lenses. There are minimal optics in this adapter, so transmission light losses are negligible.

In particular, the Canon 'cine-style' zoom lenses are suitable, which are designed to have a much larger focus latitude than video-style lenses (around 300 degrees) to enable critical focus control with a wide-open iris.

They are also designed to minimise focus 'breathing' (zoom effect whilst focussing) and maximise performance at each fixed focal length, as opposed to compact zoom lenses that are designed for portability and performance.

Also, the focus markings on the lens are very much more accurate than video-style lenses which reflect the need of the focus puller in high production-value environments.

This solution permits a quality zoom lens to be fitted to the EX-3 without using its built-in lens and allows proper focus-pulling functionality with minimum focus-breathing. It offers great low-light performance, since minimal additional optics are used and the lenses are very fast (T2.1).

It is worth mentioning that there is a small amount of crop in the image in using this combination, so a wide-angle lens is slightly zoomed-in, so be aware of this.

HD Prime lenses

Whilst HD zoom lenses offer very good performance over a range of focal lengths, this versatility comes at a cost. They are never as fast as their equivalent prime lenses (as the lenses contain more glass), and their optical performance is never as good as Prime lenses.

HD Prime lenses usually come in sets of 5 or 6 lenses of discrete focal lengths and VMI carry HD Primes by Canon and Zeiss. Each lens is designed to be optically maximised at its focal length and has measurably superior performance compared to the equivalent zoom in terms of barrel distortion, chromatic aberration and lens breathing.

Most importantly, the reduced number of optical elements compared to a zoom usually makes primes significantly faster than the equivalent zoom lens. For example, the Zeiss DigiPrime HD Prime lenses and Canon FJ HD Primes have a speed of T1.5, which is almost a stop faster than the equivalent Canon cine-style HD zoom lenses which are T2.1.The colour rendition of the Canon and Zeiss primes match closely with the Canon cine-style zoom lenses (within 150K), so are often used together without issue.

Whilst the prime lens is always going to be better than the zoom, it is important to emphasise that modern zoom lens performance is still very good and they are frequently used for high end productions. Their quality and convenience when compared to HD Primes (which come at a significant cost premium), must carefully balance the improvement in performance against the additional cost. One for the DoP and Producer to discuss.

Ultimately, the choice of which lenses to use is very much a question of personal, budgetary and aesthetic choice.

CONCLUSION

It is no longer the case that in order to shoot with a shallow depth of field, you need to shoot on large format film cameras or large sensor digital cameras.

The size of the sensor/negative affects both the viewing angle and depth of field of the image; however using a 35mm adapter onto a smaller format digital camera will display the same image with the same depth of field as using 35mm.

The availability of 35mm adapters has broadened access to budget cinematographers universally and there are many options at many price points.

35mm adapters come in many different shapes and sizes and these can work very well with a multitude of cameras with a suitable adapter to narrow the depth of field but there are some drawbacks to using them and particularly the cheaper adapters which are not very robust.

The RED One camera shoots in a native 35mm-sized format and achieves a 35mm viewing angle and depth of field without the need for a 35mm adapter.

There are several ranges of 35mm lenses available, most of which are very expensive to buy/hire. Stills lenses are an option but there are many drawbacks to using these for electronic film production.

It is crucial to understand that lens & format choice make a massive impact on production value; and that selecting the right combination of lenses and adapter will influence both the look and options available to the Cinematographer.

Lower cost stills lenses can be used but the functionality of using certain lenses will introduce some limitations during production.

If you are using the Sony EX-3, then you can fit a ½”-2/3” adapter in place of the standard lens and then fit either HD Primes or HD zooms which can afford excellent production values and at the same time standardise functionality of operation for follow-focus etc.

HD cine-style zoom lenses are capable of greater production values than video-style zooms due to superior optical and mechanical design & construction.

HD Prime lenses are capable of a more shallow depth of field than using HD zoom lenses but using Primes slows down the pace of Production compared with using Zooms, as frequent lens changes & re-collimation will take time.

These adapters and strategies can change the look of your programme enormously and with so many options available, these need not break the bank. Some of the low-cost systems can be a bit fiddly to set up and are too lightweight for reliable handling, so considerable care is required during operation.

My advice is to test your preferred combination prior to full production to ensure that you are comfortable with it.

Do be aware that shooting with a shallow depth of field means that your focus is critical: ensure that you shoot with a good HD display; check your focus often and if at all possible employ a good and experienced focus puller!

Barry Bassett,
Managing Director, VMI February 2010

Appendix

WHAT AFFECTS THE DEPTH OF FIELD

Effect of Iris on the Depth of Field

Many years ago at school, we made a pinhole camera. This was a magnificent experiment because it illustrated the relationship between depth of field and the size of iris beautifully.

You can make a pinhole camera very easily like this:

Take a cardboard box and cut one side of the box off.

Stick a sheet of tracing paper over the open side with tape.

Make a small hole in the side opposite the tracing paper.

Point the hole towards a window on a bright day

In doing this, you will see a perfectly focussed image (upside down) projected on the tracing paper.

What this illustrates is:

An infinitely small iris (hole) has an infinite depth of field, since the entire image will be in focus.

It also illustrates why the quality of lens of a very small iris is not at all important, since you have no more basic lens than just a hole and this can deliver perfect pictures!

Taking this argument a stage further, explains how mini DV cameras equipped with very basic, very cheap lenses, can produce excellent images on sunny days – since in a well-lit environment, you will shoot with a very small iris.

Contrary to this example is what happens when you shoot in low light. In low light, you must open the iris considerably and in doing so, the depth of field becomes much shallower. Poor quality lenses struggle when used in these testing conditions.

A practical example of this is a glasses-wearers difficulty whilst driving at night. The short-sighted nature of the person means that his/her eye lenses are slightly imperfect, or rather his/her lenses are slightly imperfect. Driving at night in low light conditions causes the irises to be wide-open to let in maximum light and the wide iris causes the depth of field to be very shallow. With the imperfect nature of the lenses, these challenging conditions cause the viewers sight be blurred when the irises are wide-open, yet during the day these same eyes give perfectly focussed images.

This also explains why mini DV camcorders equipped with cheap lenses shoot lovely images during the day, yet give soft images when shooting in drama-type situations in low light with a wide-open iris.

It also helps to explain why DoPs are so passionate about lenses because they perform well in all situations and why really great lenses are so reassuringly expensive!

THE EFFECT OF SENSOR SIZE

The Size of Sensor and effect on image size

The size of the sensor will affect the image angle of view, so that a 25mm Prime lens will look different if viewed on a variety of image formats.

Thus a 25mm lens will have a mid shot when used on 35mm film (HDTV 1.78:1 16:9 aspect ratio), close up on HD Camcorders and big close up on smaller semi-professional, 'prosumer' camcorders such as EX-3 and Z1 etc which have 1/2" sensors and 1/4" sensors respectively.

This explains therefore why if you mount an HD lens onto a ½? camcorder (such as Sony PDW-F355) without an optically corrected mount, that a wide angle acts like a telephoto and why the focal lengths of wide angle lenses of ½? lenses are always smaller than those used for 2/3" lenses.

Conversion of focal lengths between camera formats

Even though lenses are designed to work with different negative and sensor sizes, the convention is that lenses are still referred to by their focal lengths and/or also their zoom ratios in the case of zoom lenses.

A very useful trick to know is that to convert 35mm focal lengths to 2/3", just divide by 2.5. and to convert Super16 to 2/3", divide by 1.6.

Thus a 25mm PL mount film lens has the same field of view as a 10mm 2/3" lens.

The same lens in Super16 has an equivalent focal length of 16mm and has the same field of view as a 10mm 2/3" lens.

Size of Sensor and the effect of Depth of Field

The size of the sensor also greatly influences the Depth of Field.

Simply, the larger the sensor or negative, the narrower is the depth of field.

The ubiquitous 'film-look' has a shallow depth of field and is called this because this is easy to perform when shooting on a 35mm negative. As the size of the negative or digital sensor is reduced, so the depth of field commensurately increases for the equivalent shot and the same iris settings.

Thus, a Broadcast HD Camcorder with a 2/3" CCD sensor under the same conditions has a larger depth of field than a 35mm camera and an HDV prosumer camera with a 1/3" CCD has a larger depth of field still.

This also explains why miniDV Camcorders always shoot beautiful images with loads of depth of field and why a shallow depth of field is almost impossible to achieve without using a 35mm adapter.

The larger the sensor (or negative), the shallower is the depth of field for given conditions.

RED cameras have a 35mm-sized CMOS sensor which uses the same lenses as 35mm and these use a conventional motion-picture film lens PL mount as standard; Of these 3 groups, this is the largest sensor size and for the same conditions achieves the shallowest depth of field.

Broadcast HD Camcorders, such as the Sony HDW-F900R, Panasonic Varicam and others have a 2/3" CCD blocks and use 2/3" B4 lenses. There is a wide range of lenses available for this lens mount including Standard Definition and High Definition lightweight ENG lenses and cine-style cinematography lenses plus film lens adapters.

'Prosumer' cameras use sensors smaller than this including 1/3? and ½? CCD or CMOS sensors.

What do the numbers on the lenses mean

Traditionally, film lenses are known by their focal lengths only 14mm T1.3, 16mm T1.3 etc and the film zooms also by their focal ranges – e.g. 15-40mm T2. The sensitivity of the lens as already explained is critical in understanding how much light the lens will transmit to the negative and is an essential aid for the DoP to be able to manipulate Depth of field.

Video lenses have a different terminology and have a format whereby the first number refers to the zoom multiple of the lens and the second number is the minimum focal length of the lens.

For example an HD Wide angle lens has the label: HJ11x4.7BIRS

This means that the lens works over the range 4.7mm – 51mm (4.7*11=51.7mm)

Thus a long HD Canon cine-style lens has the label: HJ21x7.5KLL

This means that the lens works over the range 7.5mm – 157mm (7.5*21=157mm)

The KLL suffix means that this is a cine-style lens.

Motion Picture Film Lenses

Zeiss SuperSpeed T1.3 series lenses are a very fast set of PL mount lenses which have recently been superseded by the newer Zeiss UltraPrime and MasterPrime series.

These are an older generation speed of which the Mk III are the best set to use. In spite of this, these are very fast lenses (T1.3), and their compact size and light weight makes these very popular in combination with the P+S Technik Pro35 lens adapter.

The standard set includes an 18mm, 25mm, 32mm, 50mm and 85mm; all are T1.3.

A drawback to these lenses is that their relatively long minimum focus distance means that for commercials (especially pack shots), the UltraPrimes and MasterPrimes are sometimes preferred. Zeiss UltraPrime T1.9 series is the later version of the Zeiss SuperSpeed lenses. The same Zeiss precision optics and closer focussing distance than the older SuperSpeeds make this a very popular lens.

Zeiss UltraPrime T1.9 series is the later version of the Zeiss SuperSpeed lenses. The same Zeiss precision optics and closer focussing distance than the older SuperSpeeds make this a very popular lens.

The conventional set includes 18, 25, 35, 50 & 75 all T1.9.

Zeiss MasterPrime T1.4 series are faster than the Zeiss UltraPrime series and this makes them more expensive to buy and hire than the UltraPrimes. The same Zeiss attention to detail and quality precision optics ensures that these are both very popular lens choices for DoPs.

The conventional set includes 18, 25, 35, 50 & 75 all T1.4.

Cooke S4 T2 series lenses are also a great favourite with DoPs because they are not as “clinically” precise as Zeiss optics. Cooke lenses are often described to have a 'beautiful softness that is missing in Zeiss lenses'. Whatever your preference, they look beautiful and have a speed rating of T2.

RED recently produced a set of Cooke RED lenses which have some RED markings on them. Cooke advise that these have identical housings and markings, the cost of purchase is the same and the decision upon ordering them is whether you want the RED or Black markings!

The conventional Cooke S4 set includes 18, 25, 35, 50 & 75 all T2

The Cooke 'RED' set is frequently supplied with a short zoom (15-40 T2) plus a 50mm, 75mm & 100mm T2.

Other lens manufacturers exist such as Panavision who make the Primo range and also Angenieux who make the world-renowned Optimo zoom lenses and others. I have only concentrated on the mainstream film lens models commonly available.

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